Such a monitoring device for monitoring and displaying the state of the circulation of a patient is well known from WO 2009/094700 A1. The monitoring of the circulatory function of patients is a central task in intensive care. The monitoring involves the recording of various relevant parameters with sensors in order to derive variables therefrom such as various blood pressure values, blood volume pulses, cardiac output, heart rate, oxygen concentrations, etc. Physicians or medical staff then have to get an idea from these variables of whether the state of the circulation is within a physiologically normal range or whether the circulation is in a critical state with possible malfunctions such that countermeasures shall be taken. A countermeasure may be the administration of additional volumes, e.g., infusion of saline solution, or the administration of various drugs, e.g., of vasoconstricting or vasodilating drugs, or of drugs which have an effect on the activity of the heart. The physician or the medical staff must decide which of the measures are to be taken and in which direction on the basis of a larger number of variables related to the state of the circulation because of predefined strategies and empirical values.
These variables related to state of the circulation can only be interpreted with difficulty in their entirety and in their interaction such that the decision on taking therapeutic countermeasures and the type of therapeutic countermeasures is a complicated problem for the medical staff. For this reason, approaches have already been provided to derive variables from the measured variables of the circulatory function and to display them on a display device, which makes the state of the circulation intuitively more easily recordable. Among other things, it is suggested in the above-mentioned publication WO 2009/094700 to determine the mean systemic filling pressure Pms and the cardiac efficiency Eh as derived variables and display them in a system of coordinates with the mean systemic filling pressure and the cardiac efficiency as axes of coordinates. The system of coordinates does not have to be a Cartesian system in this case, but rather may also be implemented by two parallel, adjacent or otherwise shown axes of coordinates, at which the current values of both variables are shown.
In the cited publication, the mean systemic filling pressure Pms is derived by the following equation:Pms=a·RAP+b·MAP+c·CO  [1]in which a and b are predetermined factors and c is a factor, which depends on person-specific data (e.g., age, height, gender) in a predetermined manner.
In this case, the variable RAP is the right atrial pressure, MAP is the arterial mean pressure and CO is the cardiac output, a and b are predetermined, person-independent factors, and factor c is determined by a predetermined dependence from person-specific data (e.g., age, height).
The cardiac efficiency is derived by the following equation:
                    Eh        =                                            Pms              -                              R                ⁢                                                                  ⁢                A                ⁢                                                                  ⁢                P                                      Pms                    =                                                                      a                  ·                  R                                ⁢                                                                  ⁢                A                ⁢                                                                  ⁢                P                            +                                                b                  ·                  M                                ⁢                                                                  ⁢                A                ⁢                                                                  ⁢                P                            +                                                c                  ·                  C                                ⁢                                                                  ⁢                O                            -                              R                ⁢                                                                  ⁢                A                ⁢                                                                  ⁢                P                                                                                      a                  ·                  R                                ⁢                                                                  ⁢                A                ⁢                                                                  ⁢                P                            +                                                b                  ⁢                                                                          ·                  M                                ⁢                                                                  ⁢                A                ⁢                                                                  ⁢                P                            +                                                c                  ·                  C                                ⁢                                                                  ⁢                O                                                                        [        2        ]            If the heart is working too weakly, the RAP value increases, which leads to a decrease in the cardiac efficiency Eh. If the heart stops beating, all pressures are essentially equal to the mean systemic filling pressure Pms such that the cardiac efficiency Eh drops essentially to 0. Further connections and background are described in the article “Therapeutic Control of the Circulation” by W. G. Parkin et al., Journal of Clinical Monitoring and Computing 2008, 22:391-400.
It is also possible in this connection to display the state values of the pair of values Pms and Eh at consecutive points in time, e.g., as a sequence of points in a system of coordinates so that the course of development of the state of the circulation is visible.
An artificial ventilation with positive-pressure ventilation must often also be carried out in patients in intensive care units. It has been found that the monitoring of the state of the circulation described in the introduction with determination of the mean systemic filling pressure and the cardiac efficiency and the display thereof does not lead to satisfactory and reproducible results in patients with positive-pressure ventilation.